Optical fiber inspection device

ABSTRACT

The present invention provides an inspection system for inspecting a surface of an optical specimen. The inspection system includes an optical testing device having a main body and an optical axis. The optical testing device includes an optical imaging system housed in the main body. The optical imaging system includes imaging components for acquiring a microscope visual image and for acquiring at least one interference fringe image of the surface of the optical specimen. The optical testing device also includes a translational mechanism housed in the main body and configured to allow linear movement of the optical imaging system and to prevent off-axis movement of the optical imaging system.

The present application is based on and claims the benefit of U.S.provisional patent application Ser. No. 60/540,476, filed Jan. 30, 2004,the content of which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to an optical testing device. Moreparticularly, the present invention relates to an optical testing deviceused for inspection of optical specimens.

BACKGROUND OF THE INVENTION

To join two fibers or fiber optic connectors together, the quality of afiber endface or fiber connector endface needs to meet certain standardsto maximize coupling efficiency and ensure proper operation of the fiberor fiber connector. Generally, a fiber endface or fiber connectorendface has a desirable geometry or topography as well as an acceptablesurface quality. A desirable surface geometry and acceptable surfacequality is usually achieved through an optical polishing process andtested by one or more special optical instruments to verify that theendface meets certain standards.

Different optical instruments have been employed to inspect the endfaceof a fiber or fiber connector. Examples include optical microscopes andinterferometric techniques. Optical microscopes magnify undesirablesurface defects. Interferometric techniques utilize principles ofoptical interference to generate a fringe pattern representing thesurface profile being inspected. These optical instruments, however,tend to be large, expensive and require a great amount of time toinspect an endface surface. These limitations make it difficult forusers of polishing mechanisms to efficiently test and retest fiber orfiber connector endfaces.

For example, to inspect a surface of an endface using opticalinstruments known in the art, the surface should be precisely alignedwith respect to the optical instrument. In general, high precisionalignment stages are used to manipulate, align and focus the testsurface. Manipulation and alignment of a fiber optic or fiber connectorendface can be difficult if the initial position of the testing surfacedeviates from its nominal position. Furthermore, the existence of amulti-axis adjustment mechanism used to align the test surface increasescomplexity, cost of the instrument and introduces an inherent need tofrequently readjust the system. Most optical instruments used forinspecting fiber or fiber connector endfaces are fairly large, bench-topinstruments designed for static laboratory use. The size and weight ofthese devices make them impractical for portable use.

SUMMARY OF THE INVENTION

The present invention provides an inspection system for inspecting asurface of an optical specimen. The inspection system includes anoptical testing device having a main body and an optical axis. Theoptical testing device includes an optical imaging system housed in themain body. The optical imaging system includes imaging components foracquiring a microscope visual image and for acquiring an interferencefringe image of the surface of the optical specimen. The optical testingdevice also includes a translational mechanism housed in the main bodyand configured to allow linear movement of the optical imaging systemalong the optical axis and to prevent off axis movement of the opticalimaging system.

The present invention further provides a method of inspecting a surfaceof an optical component. The method includes providing a portableoptical testing device configured to receive and inspect an opticalspecimen while the optical specimen is attached to a different opticalprocessing system. A magnified visual image of the surface of theoptical specimen is acquired and a surface defect analysis is performedon the magnified visual image of the optical specimen. In addition, atleast one fringe image of the surface of the optical specimen isacquired and a surface topography analysis is performed on the at leastone fringe image of the optical specimen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of an inspection system inaccordance with an embodiment of the present invention.

FIG. 2 illustrates an enlarged perspective view of an optical testingdevice in accordance with an embodiment of the present invention.

FIG. 3 illustrates a sectional view of an optical testing device inaccordance with an embodiment of the present invention.

FIG. 4 is a flowchart illustrating steps associated with processing amagnified image in accordance with an embodiment of the presentinvention.

FIG. 5 illustrates an example of a magnified image in accordance with anembodiment of the present invention.

FIG. 6 illustrates a plan view of a beamsplitter in accordance with anembodiment of the present invention.

FIG. 7 is a flowchart illustrating steps associated with processing atleast one fringe image in accordance with an embodiment of the presentinvention.

FIG. 8 illustrates an example of a fringe image in accordance with anembodiment of the present invention.

FIG. 9 illustrates an example of a topographical image that is generatedbased on an acquisition of at least one fringe image in accordance withan embodiment of the present invention.

FIG. 10 illustrates a perspective view of an optical imaging system anda translational mechanism in accordance with an embodiment of thepresent invention.

FIG. 11 illustrates a perspective view of a flexible plate in anon-deformed position and a deformed position in accordance with anembodiment of the present invention.

FIG. 12 illustrates a perspective view of an optical testing device withits kinematic interface removed in accordance with an embodiment of thepresent invention.

FIG. 13 illustrates an exploded perspective view of a kinematicinterface in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although embodiments of the present invention will be described in thecontext of testing an endface surface of optical fibers or fiberconnectors, the present invention is applicable to other types ofmicroscopic optical surfaces, such as lens arrays and other suitablesurfaces.

FIG. 1 is a perspective view of an inspection system 100 in accordancewith an embodiment of the present invention. Inspection system 100includes an optical testing device 102 coupled to a computing device 104preferably by a cable 106. Optical testing device 102 is configured toreceive and fixedly secure an optical specimen 105, such as an opticalfiber or fiber connector endface, for inspection. Computing device 104includes software configured to display measurement and inspectionresults and to initiate various electrical functions of optical testingdevice 102. Optical testing device 102 includes an interface 107 adaptedto communicate with computing device 104. In one embodiment, interface107 can be a Universal Serial Bus (USB) 2.0 interface. Such an interfaceallows optical testing device 102 to operate without an external powersupply. Power can be supplied to optical testing device 102 throughcable 106 and interface 107 from computing device 104. It should benoted that optical testing device 102 is not limited to any particulartype of interface 107 nor any particular type of power supply. Forexample, interface 107 can be adapted to receive wireless signals fromcomputing device 104 as well as include other types of interfaceconfigurations. In addition, power can be supplied to optical testingdevice 102 by a storage battery or other type of device.

FIG. 2 illustrates an enlarged perspective view of optical testingdevice 102. Optical testing device 102 includes a base 108, a main body110 and a kinematic interface 112. Main body 110 is centered about anoptical axis 139. However, those skilled in the art should recognizedthat optical axis 139 can be placed in other positions with respect tomain body 110. Base 108 is a removable base and supports main body 110in an upright direction. When base 108 is attached to main body 110,optical testing device 102 can be supported on a level surface. Mainbody 110 has a slender shape that includes a grip portion 111 such thata user can easily grip and carry optical testing device 102 for portableuse. Although FIG. 2 illustrates main body 110 as a cylindrical body, itshould be noted that other shapes can be implemented. As illustrated inFIG. 2, kinematic interface 112 is preferably a detachable assemblylocated near the object plane (i.e. the area where the optical specimenis attached to the optical testing device) and configured to receive andretain an optical specimen, such as optical specimen 105 illustrated inFIG. 1, along optical axis 139. Kinematic interface 112 will bediscussed in more detail with respect to FIG. 13.

Main body 110 houses a plurality of interconnected electrical componentsand a plurality of interconnected imaging components. For example, mainbody 110 includes a microprocessor. The microprocessor is used inconjunction with a camera, such as an area array detector, cable 106(FIG. 1) and computing device 104 (FIG. 2). The microprocessor controlsthe function of and reports data from optical testing device 102.

FIG. 3 illustrates a sectional view of optical testing device 102 inaccordance with an embodiment of the present invention. Morespecifically, FIG. 3 illustrates a sectional view of base 108, main body110 and kinematic interface 112 of optical testing device 102. Main body110 includes optical imaging system 114. Optical imaging system 114includes imaging components bonded together with an optical compliantadhesive such that optical testing device 102 is robust and durable.Optical imaging system 114 is capable of operating in two distinctmodes. Optical imaging system 114 uses imaging components to perform oroperate in a microscope visual mode and also to perform or operate in aninterferometric measurement mode.

The imaging components of optical imaging system 114 are arranged inaccordance with a Michelson Interferometer configuration. In amicroscopic visual mode, optical testing device 102 acquires atwo-dimensional magnified image of the surface of the optical specimen(i.e. microscope visual image). In an interferometric measurement mode,optical testing device 102 acquires at least one interference fringeimage to produce a three-dimensional surface model or topographicalimage of the surface of the optical specimen. Imaging components ofoptical imaging system 114 include a beamsplitter 116, a referencemirror 118, an optical source or sources 120, illumination optics 122and imaging optics 124.

During microscope visual mode operation, optical source or sources 120produce a beam of light 129 that passes through illumination optics 122towards beamsplitter 116. For example, optical source or sources 120 canbe an LED or a plurality of LEDs. Beamsplitter 116 can be any type ofoptical component that splits a beam of light into two or more opticalpaths. In one embodiment, beamsplitter 116 can be a flat glass platehaving a coating on one side. In another embodiment and as illustratedin FIG. 3, beamsplitter 116 can be a cube having two prisms fittedtogether. Those skilled in the art should recognize that beamsplitter116 can include other types of configurations that are not explicitlydescribed. Beamsplitter 116 is discussed in further detail in accordancewith FIG. 6. At beamsplitter 116, beam 129 is split into beam 138 andbeam 140. A shutter 125, operated by an actuator 127 (illustrated inFIG. 10), is actuated into a closed position. In one embodiment, but notby limitation, actuator 127 can be a solenoid. Shutter 125 blocks beam140 from reflecting off of reference mirror 118. Beam 138 follows anoptical path along an optical axis 139 of optical testing device 102 toilluminate the surface of the optical specimen. Imaging optics 124 areused to relate the image of the surface of the optical specimen onto anarea array detector 126.

The device 102, as illustrated in FIGS. 1-3, has a rather smalldimension. In particular, but not by limitation, device 102 includes aheight that is approximately 150 mm and a diameter that is less than 200mm. For example, the diameter of device 102 can be approximately 70 mm.In addition, device 102 is rather light-weight. In particular, but notby limitation, device 102 has a weight that is less than 2.25 kg. Forexample, device 102 can be approximately 630 g.

In one embodiment of the present invention, optical testing device 102acquires a magnified image from area array detector 126 to be viewed bya user. In this embodiment, the user can subjectively determine if thesurface of the optical specimen is in compliance with specificrequirements or criteria such that further processing is unnecessary.For example, when the optical specimen is an endface of a fiber or fiberconnector, the user subjectively determines if the endface needs furtherpolishing or cleaning.

In another embodiment of the present invention, optical testing device102 acquires a magnified image from area array detector 126 to beassessed by computing device 104. In this embodiment, the user can useimage processing software located in computing device 104 to makeobjective decisions about defects on the surface of the opticalspecimen. FIG. 4 is a flowchart 400 illustrating steps associated withprocessing a magnified image acquired by optical testing device 102.

At block 402, the image processing software determines a center point ofthe surface of the optical specimen. The center point of the surface ofthe optical specimen is found by locating the circular edge of theoptical specimen and applying an image processing algorithm. FIG. 5 isan example of a magnified image of a surface 502 of an optical specimen500. FIG. 5 illustrates the designation of a center point 506. At block404, the image processing software identifies surface defects that arelocated on the surface 502 of optical specimen 500. At block 406, eachsurface defect is classified. The image processing software can classifya surface defect as a particle, a chip or a scratch. A particle is apiece of matter that protrudes above the surface 502 of optical specimen500. A chip or dig is an area where a portion of the optical specimen ismissing or is uneven with the remaining portion of the specimen. Ascratch is a long, thin chip. FIG. 5 illustrates surface defects, suchas chips or digs 508 and scratches 509, on surface 502. In addition, theimage processing software can determine the width of epoxy is ferrule. Alarge epoxy width can indicate that the diameter of the fiber is toosmall.

At block 408, the image processing software measures the size of eachclassified surface defect. For example, image processing softwaremeasures the width, length and area of the surface defects. At block410, the image processing software compares the sizes of each surfacedefect to predetermined threshold values. These threshold values can bevalues as specified by a standard of acceptability. For example, thestandard or criterion of acceptability can be commonly acceptedstandards such as international standards. Examples of internationalstandards include standards from the Telecommunication IndustryAssociation (TIA), the International Electrotechnical Commission (IEC),and/or the Telcordia standards. At block 412, the image processingsoftware determines whether the optical specimen meets the standard ofacceptability based on the comparison. If the optical specimen does notmeet the standard of acceptability, then the optical specimen is furtherprocessed and retested. For example, when the optical specimen is afiber or fiber connector, the fiber or fiber connector endface isfurther polished, cleaned and retested.

With reference back to FIG. 3, during operation in the interferometricmeasurement mode, optical source or sources 120 produce beam of light129 that is diffused and passed through illumination optics 122.Illumination optics 122 directs beam 129 towards beamsplitter 116. FIG.6 illustrates an enlarged plan view of beamsplitter cube 116 as itrelates to optical paths of optical imaging system 114 during operationin an interferometric measurement mode. Beamsplitter cube 116 includes afirst prism 128 having a first edge 130 and a second edge 131.Beamsplitter cube 116 also includes a second prism 132 having an edge134. The first and second prisms 128 and 132, typically made of glass,are aligned and adhered together with an optical compliant adhesive athypotenuse 136. Beam 129, as emitted from optical source 120 andilluminated by illumination optics 122, enters beamsplitter cube 116 atsecond edge 131 of prism 128. At hypotenuse 136, a portion 138 of beam129 is reflected through first edge 130 of first prism 128 along opticalaxis 139 towards the test surface of the optical specimen. The remainingportion 140 of beam 129 travels through edge 134 of second prism 132towards reference mirror 118.

First and second prisms 128 and 132 are assembled and aligned such thatthere is approximately a zero optical path distance difference. Forexample, in FIG. 3, the alignment and arrangement of beamsplitter 116creates two similar optical paths. Specifically, the optical distancethat beam 138 travels through prism 128, from hypotenuse 136 to firstedge 130, is approximately the same as the optical distance beam 140travels through prism 132 from hypotenuse 136 to edge 134. The twooptical paths each have a length that is within about 1.0 microns fromeach other.

Referring both to FIGS. 3 and 6, beam 138 is reflected off of a surfaceof an optical specimen that is mounted to optical testing device 110 bykinematic interface 112 and back through first edge 130 of prism 128towards hypotenuse 136. In interferometric measurement mode, shutter125, operated by the actuator (illustrated in FIG. 10), is actuated intoan open position. Shutter 125 allows beam 140 to reflect off ofreference mirror 118 and back through edge 134 of prism 132 towardshypotenuse 136. Reference mirror 118, controlled by computing device 104(FIG. 1), provides phase shifting capability on beam 140 forhigh-resolution three-dimensional surface geometry measurements. Apiezoelectric element 144 can induce a phase shift in beam 140 by movingreference mirror 118. For example, piezoelectric element 144 can expandaxially upon application of a voltage to actuate reference mirror 118.Those skilled in the art should recognize that other means can be usedto achieve a phase shift. Instant Phase Measuring Interferometrytechniques and Spatial Center techniques are examples that utilizehardware and mathematics, respectively.

At beamsplitter 116, beams 138 and 140 optically interfere or recombineand, under the correct circumstances, form interference fringes. Therecombined beam or interference fringes are imaged by imaging optics 124onto area array detector 126 for image capture and viewing. Asillustrated in FIG. 3, imaging optics 124 include a plurality of lenses.After imaging optics 124 image the interference fringes, area arraydetector 126 creates an intensity profile of each fringe pattern fordigitizing and conversion to a digital image.

Optical testing device 102 sends the fringe image data to computingdevice 104 via cable 106 for fringe image processing. A user can usefringe image processing software in computing device 104 to makeobjective decisions related to the topography of the endface of theoptical specimen. FIG. 7 is a flowchart 700 illustrating stepsassociated with processing a fringe image acquired by optical testingdevice 110 in accordance with an embodiment of the present invention.FIG. 8 illustrates an example fringe image 800 in accordance with anembodiment of the present invention.

At block 702, the image processing software measures the shape of theendface of the optical specimen. For example, a fiber connector endface,that is a fiber glued into a ferrule, needs to have a certain roundness,an apex that coincides with the center of the fiber and a certain amountof protrusion of the fiber with respect to the ferrule such that thefiber connector endface can make proper optical contact with other fiberconnector endfaces. FIG. 9 illustrates an example of a topographicalimage 900 that is generated based on the at least one fringe image 800in accordance with an embodiment of the present invention. Topographicalimage 900 illustrates fiber height 902 and the radius of curvature orroundness 904. At block 704, the image processing software determinesthe roughness of the optical specimen. For example, the roughnessdetermination can indicate the presence of a particle on the surface ofthe optical specimen. At block 706, the image processing softwarecompares the shape measurements and roughness determination topredetermined threshold values. These threshold values are valuesspecified by standards of acceptability. For example, the standards ofacceptability can be commonly accepted standards such as internationalstandards. Examples of international standards include standards fromthe Telecommunication Industry Association (TIA), the InternationalElectrotechnical Commission (IEC), and/or the Telcordia standards. Atblock 708, the image processing software determines whether the opticalspecimen meets the standards of acceptability based on the comparison.If the optical specimen does not meet these standards, then the opticalspecimen is further processed and retested. For example, when theoptical specimen is a fiber or fiber connector, the fiber or fiberconnector endface is further polished, cleaned and retested.

With reference to FIG. 3, imaging optics 124 of optical testing device110 can be configured in a plurality of optical magnifications. Forexample, the magnification can be selected from a plurality of settings,such as 7×, 10×, 12×, and 20×. The magnifications are preferablyselected with a turret device 148. Multiple fixed focal length elementsare radially located about turret device 148. Turret device 148 ismechanically rotated such that upon each rotation a different set offixed focal length optics are placed along optical axis 139. It shouldbe noted that the rotation of turret device 148 can be actuated manuallyor actuated automatically via electrical signals received from computingdevice 104. Turret device 148 can also include a turret sensor (notshown). The turret sensor senses the magnification position of turretdevice 148 such that when optical testing device 102 is acquiring imagesthe magnification is known. Therefore, optical imaging system can easilyvary magnifications of the surface of the optical specimen being imagedon area array detector 126.

In addition, optical imaging system 114 includes the ability to adjustthe focus of an image. Since the optical specimen is fixedly received(without any manipulation) by kinematic interface 112, optical imagingsystem 114 compensates the variation in height of the optical specimenand optimizes image quality of the surface of the optical specimen. Tomake adjustments, optical imaging system 114 is linearly translatedalong optical axis 139 in directions 150 with a translational mechanismwhile the optical specimen remains stationary. In one embodiment, thetranslational mechanism includes a plurality of shafts and bearings. Inanother embodiment, and as illustrated, the translational mechanism is aflex mechanism 152. Flex mechanism 152 is illustrated in detail in FIGS.10-12.

FIG. 10 is a perspective view of optical imaging system 114 and flexmechanism 152 in accordance with an embodiment of the present invention.Flex mechanism 152 includes a first flexible plate 154 positioned at afirst end 155 of optical imaging system 114 and a second flexible plate156 positioned at a second end 157 of optical imaging system 114. Firstand second flexible plates 154 and 156 are flat, spring elements. Forexample, first and second flexible plates 154 and 156 can be made of aspring steel. However, those skilled in the art should recognize thatother types of metallic and non-metallic materials that have similarproperties can be used. Each flexible plate 154 and 156 includes anouter portion 158 that is configured for attachment to main body 110(FIG. 3) of optical testing device 102 (FIG. 3) and an inner portion 160that is configured for attachment to optical imaging system 114. Outerportion 158 is connected to inner portion 160 by a plurality of wings162, of which three are shown. A motor (illustrated in FIG. 12), locatedin optical testing device 102 and preferably controlled by computingdevice 104, provides an axial force (in direction 150 illustrated inFIG. 3) to flexible plates 154 and 156. It should be noted, however,that a manually applied axial force can also be used to move flexibleplate 154 and 156. Under this axial force, flexible plates 154 and 156equally deform. FIG. 11 illustrates flexible plate 154 in both anon-deformed state as well as in a fully deformed state. The deformedstate provides a linear motion to optical imaging system 114 over arange 164. Range 164 is approximately 3 mm. It should be noted, however,that range 164 can include other values depending on the amount oftranslation that is needed.

FIG. 12 illustrates a perspective view of optical testing device 102with kinematic interface 112 (FIGS. 2 and 3) removed. FIG. 12illustrates the placement of flex mechanism 152 with respect to mainbody 110 and optical imaging system 114. In addition, FIG. 12illustrates a motor 165 configured to linearly translate optical imagingsystem 114 for focusing of optical testing device 102.

FIG. 13 illustrates an exploded perspective view of kinematic interface112 in accordance with an embodiment of the present invention. Asillustrated, kinematic interface 112 is a kinematic mount that isconnected to main body 110 of optical testing device 102 and configuredto receive, retain, and fixedly secure an optical specimen 105 (FIG. 1)for inspection without any further manipulation. Kinematic interface 112is positioned proximal to optical imaging system 114 (FIG. 3). KinematicInterface 112 includes an adapter 166 and an interface plate 168.Adapter 166 holds the optical specimen to be tested and rigidly fixesthe optical specimen to main body 110 of optical testing device 102.

In accordance with an embodiment of the present invention, adapter 166is interchangeable with other adapters such that kinematic interface 112can accept various types of optical specimens. For example, to inspectfiber or fiber connector endfaces, each interchangeable adapter isconfigured to accept one of a standard fiber connector, a custom fiberconnector and a bare fiber as used in the fiber optic industry. Forexample, different types of adapters can be made to accept differenttypes of connectors, such as, an FC connector, an FCAPC (angled physicalcontact) connector, an ST connector, an SC connector, and a SCAPC(angled physical contact) connector. Each interchangeable adapter 166 isfitted with an optical specimen-specific insert 170. It should be notedthat adapter 166 and insert 170 can be easily configured to receivevarious optical specimens outside of fiber optical specimens. Forexample, adapter 166 and insert 170 can be configured to receive lensesand arrays.

Adapter 166 and insert 170 mate to interface plate 168 through, but notby limitation, a six-point kinematic contact arrangement that utilizesat least three precision tooling balls 172. Precision tooling balls 172are radially arranged and fixed about an outer edge 173 of adapter 166and are seated in at least three “kinematic seats”. “Kinematic seats”can include any type of configuration as long as the “kinematic seats”provide two points of contact. For example and as illustrated in FIG.13, tooling balls 172 can be seated in pins 174. In another example, butnot illustrated, tooling balls 172 can be seated in a v-shaped groove.In FIG. 13, pins 174 are fixed to interface plate 168. Tooling balls 172and the “kinematic seats” are radially arranged about an outer edge 175of kinematic interface 112. Magnets 176 are radially arranged andmounted to an outer edge 175 of interface plate 168 and impart anequivalent pull on tooling balls 172 to form a consistent load on theadapter 166. This configuration allows easy swapping between differenttypes of adapters for receiving different types of optical specimens.

An interchangeable adapter 166 is precisely aligned during fabricationto ensure that the position of tooling balls 172 are within apredetermined tolerance of the nominal position of an optical specimen.Such alignment during fabrication of each adapter results in repeatedpositioning of an optical specimen that is less than 2 microns away froma prior position. In addition, interface plate 168 is aligned to mainbody 110 in accordance with optical axis 139.

Each interchangeable adapter 166 can also serve as an interfacecomponent for existing optical systems, such as polishing systems. Forexample, in one application, a fiber or fiber connector is mounted to apolishing system and can be tested by optical testing device 102 withoutdisconnecting the fiber or fiber connector from the polishing mount. Inthis example, adapter 166 is fixed and aligned to the polishingmechanism and optical testing device 102 is joined to the polishingmechanism through interface plate 168. Such a configuration allows auser to inspect the endface of the fiber or fiber connector withoutremoving the fiber or fiber connector from the polishing mechanism forpositioning in kinematic interface 112. Instead, the fiber or fiberconnector remains on the polishing mechanism and the portable propertiesof optical testing device 102 allow inspection of the endface of thefiber or fiber connector. It should be noted that polishing mechanismsare not the only type of optical processing system in which an opticalspecimen can remain attached while optical testing device 102 does aninspection. Other types of optical processing systems are within thescope of the present invention, such as cleaning mechanisms.

Although not specifically illustrated in FIGS. 1-13, optical testingdevice 102 performs a set of calibrations such that the inspectionresults of the microscope visual mode and the interferometricmeasurement mode are accurate. In order to calibrate optical testingdevice 102, a specially fabricated adapter is fitted with interfaceplate 168 of mount 112. The specially fabricated adapter includes acalibration specimen. The calibration specimen comprises a sphericalpiece of which the topography and surface quality is known. For example,the calibration specimen can be a lens or other three-dimensional ortwo-dimensional target. A two-dimensional target can be used tocalibrate microscope distortion and other elements of microscope use,while a three-dimensional target can be used to calibrate elements offringe images. Optical testing device 102 performs an inspection on thecalibration specimen and the optical testing device is calibratedaccordingly. In addition, optical testing device 102 also performs aphase-shift calibration such that reference mirror 118 is moved anappropriate distance that coincides with an appropriate phase-shift ofthe beam of light reflecting of the reference mirror.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. An inspection system for inspecting a surface of an optical specimen,the system comprising: an optical testing device having a main body andan optical axis, the optical testing device comprising: an opticalimaging system housed in the main body, the optical imaging systemhaving imaging components for acquiring a microscope visual image andfor acquiring at least one interference fringe image of the surface ofthe optical specimen; and a translational mechanism housed in the mainbody and configured to allow linear movement of the optical imagingsystem along the optical axis and to prevent movement of the opticalimaging system in any direction perpendicular to the optical axis. 2.The inspection system of claim 1, further comprising a computing deviceremotely located and coupled to the optical testing device, thecomputing device configured to process surface defects and surfacetopography of the optical specimen based on the microscope visual imageand the at least one interference fringe image of the optical specimen.3. The inspection system of claim 2, wherein the optical device ispowered by the computing device.
 4. The inspection system of claim 3,wherein the computing device powers the optical testing device through aUniversal Serial Bus (USB) interface.
 5. The inspection system of claim1, wherein the optical specimen is located in alignment with the opticalaxis and in a fixed position.
 6. The inspection system of claim 5,wherein the optical device further comprises a kinematic interfaceconnected to the main body and located proximate the optical imagingsystem, the kinematic interface configured to receive and rigidly securethe optical specimen.
 7. The inspection system of claim 6, wherein thekinematic interface comprises: an interface plate coupled to the mainbody of the optical device; and an interchangeable adapter configured tobe rigidly coupled to the interface plate and configured to receive theoptical specimen for inspection.
 8. The inspection system of claim 1,wherein the translational mechanism comprises a first flexible platepositioned at a first end of the imaging system and a second flexibleplate positioned at a second end of the imaging system, wherein thefirst flexible plate and the second flexible plate are deformable uponlinear translation along the optical axis of the optical imaging system.9. The inspection system of claim 8, wherein the first and secondflexible plates comprise an inner portion attached to the opticalimaging system and an outer portion attached to the main body.
 10. Theinspection system of claim 8, wherein the optical device furthercomprises a motor configured to deform the first and second flexibleplates and thereby linearly translate the optical imaging system alongthe optical axis.
 11. The inspection system of claim 8, wherein theoptical device further comprises a manually actuated mechanismconfigured to manually deform the first and second flexible plates andthereby linearly translate the optical imaging system along the opticalaxis.
 12. The inspection system of claim 1, wherein the optical testingdevice comprises a plurality of optical magnifications.
 13. Theinspection system of claim 1, wherein the optical imaging systemcomprises a beamsplitter cube.
 14. The inspection system of claim 1,wherein the optical imaging system comprises an actuator, the actuatorconfigured to move a shutter into a closed position during acquisitionof the microscope visual image and into an open position duringacquisition of the at least one interference fringe image.
 15. Theinspection system of claim 1, wherein the main body of the opticaldevice includes a grip portion such that a user can hold and carry theoptical device.
 16. The inspection system of claim 1, wherein theoptical device comprises a weight that is less than 2.25 kg.
 17. Theinspection system of claim 16, wherein the optical device comprises aweight of approximately 630 g.
 18. The inspection system of claim 1,wherein the optical specimen is one of a fiber endface and a fiberconnector endface.
 19. An inspection system for inspecting a surface ofan optical specimen, the system comprising: an optical testing devicehaving a main body and an optical axis, the optical testing devicecomprising: an optical imaging system housed in a main body, the opticalimaging system having imaging components for acquiring a microscopevisual image and for acquiring at least one interference fringe image ofthe surface of the optical specimen; and a kinematic interface connectedto the main body of the inspection system and proximate the imagingsystem, the kinematic interface configured to receive and rigidly securethe optical specimen in alignment with the optical axis for inspection.20. The inspection system of claim 19, further comprising atranslational mechanism housed in the main body and configured to allowlinear movement along the optical axis of the optical imaging system.21. The inspection system of claim 20, wherein the translation mechanismcomprises a first flexible plate positioned at a first end of theimaging system and a second flexible plate positioned at a second end ofthe imaging system, the translational mechanism configured to move theimaging system linearly along the optical axis.
 22. The inspectionsystem of claim 19, wherein the kinematic interface comprises: aninterface plate coupled to the main body of the optical device; and aninterchangeable adapter configured to rigidly couple to the interfaceplate and receive the optical specimen for inspection.
 23. Theinspection system of claim 22, wherein the kinematic interface furthercomprises: at least three magnets radially arranged about an outer edgeof the interface plate; and at least three tooling balls radiallyarranged about an outer edge of the interchangeable adapter, each magnetconfigured to exert an equivalent pull on each tooling ball.